Proe. indian Aead. Sci., Vol. 85 B, No. 2, 1977, pp. 57-66. Petiolar anatomy of certain members of Bignoniaceae M. L. TRIVZDI, SHebA AND VEronA ~A Department of Botany, Punjabi University, Patiala 147002 MS received 1 September 1976; in revised form 14 October 1976 ABSTRACT The petiolar anatomy of sixteen species belonging to iourteen genera of Bignoniaceae has been studied. Two aspects, namely, the vascular pattern in the slender part of the petiole and the mode of vascular supply from the primary rachis to leaflets or secondary rachii, are taken into consideration. On the basis of the ~asculature as seen in tran.,ecticn of the slendeI part, four main types of petioles have been recognized, while thereare three patterns of vascular supply. A key also has been devised to identify these sixteen species. 1. INTRODUCTION PETIOLAR anatomy has received considerable attention of anatomists from time to time. One of the most comprehensive works on this aspect is by Watari} on Leguminosae. Howard ~' also has surveyed the petiole vasculature i n a large number of dicot families and found this structure to be of great taxonomic value. Carlquist 3 favoured correlated study of node-petiole structure. Howard ~ also advocated the study of the stem node-leaf-continuum The present study deals with the petiolar anatomy of certain Bignoniaceous members. The nodal anatomy of some members has already been studied by the present authors. 5 2. MATERIALSAND METHODS Materials for the present study were collected from plants growing in the Botanical Garden and the University Campus. The growing shoot tips with young leaves were fixed in F.A.A. Normal procedures for paraffin embedding were followed. Transections were obtained at 8-10 t, and stained with safranin-light green combination. The following species were studied: 57 58 M. L. TRIVEDI, SHAILAJA AND VEENA KHANNA 1. Adenocalymma alliaceum (Lain.) Miers. 2. Bignonia purpurea Lodd. 3. Campsis grandiflora K. Schum. 4. Doxantha unguis-cati Rehd. 5. 1-Iaplo- phragma adenophyllum (Wall) P. Dop. 6. Jacaranda mimosifolia D. Don. 7. Kigelia pinnata DC. 8. MiUingtonia hortensis Linn. 9. Parmentiera cerifera Seem. 10. Pyrostegia venusta (Ker-Gawl.) Miers. 11. Spathodea campanulata Beauv. 12. Stenolobium stans Seem. 13. Tabebuia argentia Britt. 14. Tabebuia pentaphylla Hemsl. 15. Tecoma capensis Lindl. 16. Tecoma jasminoides Schum. 3. OBSERVATIONS Bignoniaceae members bear compound leaves. It is a very impor- tant character by which the family can be distinguished from other associated families of the order Personales. The leaves are pinnately compound with odd number of pirmae borne on primary, secondary or even tertiary rachii. Palmately compound and simple leaves are also met with in a few cases. The petiolar anatomy has been studied from two different viewpoints. Firstly, to see the topographic arrangement of the vascular bundles in the slender part of the petiole, slightly below the attachment of first pair of leaflets. Secondly, to trace the pattern of vascular supply from main rachis to leaflets or the secondary rachii, as the case may be. The following types are observed on the basis of the number of vascular bundles and their topographic a~:'angement, in the petiole. TYPE [ WITH FIVE VASCULAR BUNDLES" In Pyrostegia venusta three traces (one medium and two laterals) depart from a common gap irt the stem to enter the base of the petiole. The two lateral traces soon bifurcate and thus five traces are formed. In the middle of petiole, the transection shows five bundles arranged in such a manner that they can be designated as one dorsal (DB), two laterals (LB, LB') and two ventrals (VB, VB'). Thus, the arrangement is expressed as 1 + 2 + 2 (figure 1). TYPE II WITI-I SEVEN VASCULAR BUNDLES: In Tecoma jasminoides five traces pass througk a common gap and enter the base of the petiole. A little higher up, the lower laterals sh,ow bifurcation resulting in seven dis- tinct vascular bundles. These are labelled as one dorsal (DB), four laterals (LBI, LB2 and LBI', LB./) and two ventrals (VB, VB'). Thus, the topo- graphic arrangement is 1 + 4 + 2 (figure 2). A similar topograpkic arrangement (1 + 4 + 2) is met with in Doxantha ungius-cati, Bignonia purpurea, Stenolobium stans arid Campsis grandiflora where the nodal condition is unilacunar, triple-traced. This arrange- PETIOLAR ANATOMY OF BIGNONIACEAE 59 ment is achieved by the bifurcation of lateral traces and further forking of the lower derivatives. Thus, seven vascular bundles are formed. TYPE III WITH THIRTEEN VASCULAR BUNDLES: In Tabebuia pentaphylla the transection through the nodal region shows three traces passing through the single gap. The lateral traces bifurcate and ultimately the number of vascular bundles in the middle of the petiole increases to thirteen. These have been labelled as one dorsal (DB), eight laterals (LB1, LB2, LB3, LB4 and LB(, LB~', LB3', LBj)and four ventrals (VB1,VB2 and VBI', VB2') 1 ÷ 8 + 4 arrangement (figure 3). A similar topographic arrangement (1 ÷ 8 + 4)is observed in Adeno- calymma alliaceum, Millingtonia hortensis and Kigelia pinnata. In tIaplo- phragma adenophyllum the petioles he.ve 3 + 6 + 4 arrangement (figure 4). TYPE IV WITH FIFTEEN VASCULAR BUNDLES" In Spathodea companulata at the nodal region the procambial arc with seven vascular traces enter the base of the petiole. Later, a pair of laterals on either side is added from the axial cylinder to supplement the vascular supply of the petiole. Higher up, the number of vascular bundles becomes 15 which are labelled as dorsal , ! ~ -'I 15 ~, ~. , 7 Figures 1-7.1. T.S. petiole of Pyrostegia venusta. 2. T.S. petiole of Tecoma ]asminoides. 3. T.S. petiole of Tabebuia pentaphylla. 4. T.S. petiole of Haplophragma adenophyllum. 5. T.S. petiole of Spathodea campanulata. 6. T.S. petiole of Tabebuia argentia. 7. T.S. petiole of Tecoma capensis. B2~eb. 77 60 M. L. TRIVEDI, SHAILJA AND VEENA KHANNA (DB), eight laterals (LB1, LB~, LB3, LB4 and LBI', LB(, LB3', LB4') and six ventrals (VBx, VB2, VBz and VBI', VB(, VB3'). Thus, the arrangement can be expressed as 1 + 8 + 6 (figure 5). In Tabebuia argentia, Jacaranda mimosiJolia and Tecoma capensis also the petioles have fifteen vascular bundles. Howevel, the topographic arrangement in T. argentia is 3 + 6 + 6 (figure 6) while in the other two members the arrangement is 3 + 8 + 4 (figure 7). On the basis of the manner of vascular supply to the leaflets(or secondary rachii in ease of multipinnate leaves) the following three types have been recognised : 1. L AND V TYPE: In Tecoma jasminoides, as already describeds there are seven vascular bundles (figure 2). The supply for the first pair of leaflets is given off from the laterals (LB2, LB~') which enter as such accompanied by vascular traces from ventrals (VB and VB') on their res- pective sides (figure 8). Thus only five vascular bundles are left in the main rachis after the supply to the first pair of leaflets. The remaining vascular elements of the ventrals bifurcate and the upper half of each ventral takes lateral position (figure 9). The supply for the second pair of leaflets is given off in a manner similar to the first one, but here the laterals are the product of the ventrals themselves (figure 10). The remaining vascular elements, i.e., dorsal (DB), two laterals (LBa, LBI') and ventrals (VB, VB') enter the terminal leaflet (figure 11). In the present investigation, a large number of plants show this type of vascular supply where the laterals and the ventlals are the contributors. Of these, Pyrostegia venusta has five vascular bundles in the petiole while Doxantha unguis-cati, lJignonia purpuria, Stenolobium stans and Parmentiera cereifera have seven. In Adenocalymma alliaceum, Tabebuia pentaphylla and Millingtonia hortensis also, where the transection of petiole show, thirteen vascular bundles, the supply departs from laterals and ventrals only. A similar vascular pattern is met with in Spathodea eampanulata, Tecoma capensis and Tabebuia argentia where fifteen vascular bundles are observed in transection of petiole. 2. L Alqo R TYPE: A transection through the middle of the petiole of Jacaranda rnimo~ifolia reveals the presence of fifteen vascular bundles. These are labelled as three dorsals (DB1, DB, DBI'), eight laterals (LBz, LB2, LB3, LB4 and LBx', LB~', LB3', LB~') and four ventrals (VB1, VB~ and VB(, VB~'). Beside~, two ridge bundles (RB, RB') are seen in the ridges (figure 12). PETIOLAR ANATOMY OF BIGNONIACEAE 61 I J~ F~. e-, , ~*~ I, 4 G 17 Figures 8-17. 8, 9. Transections through primary rachis of Tecoma jasminoides at different levels of first nodule. 10. T.S. through the racbis at second nodule of Tecoma jasminoides. 11. T.S. through the base of petiole of the terminal leaflet of Tecoma iasminoides. 12 T.S. petiole of .Jacaranda mimosifolia. 13. T.S. primary rachis of J. mimosifolia at first nodule. 14. T.S. petiole of Campsis grandiflora. 15, 16. T.S. primary rachis of C. grandiflora at different levels of the first nodule. 17. T. S. through the base of petiole of terminal leaflet of C. grandiflora. 62 M.L. TRIVEDI, SHAILJA AND VEENA KHANNA The supply for the first pair of secondary rachii departs from the lateral (LB4) and ridge bundle RB on one side and from LB4' and RB' on the other. The lateral LB4 and LB4' leave the ring as such while only traces from the ridge bundles accompany them (figure 13). After the supply for the first pair of secondary rachii has departed, the dorsal bundle DB trifur- cares. Thus, again the number of vascular bundles in the intemodular region is restored to fifteen. The supply at the subsequent nodules departs in a similar manner, i.e., from the lowermost lateral accompanied by traces from the ridge bundle.